1. Field of the Invention
The present invention relates to a capacitor for a semiconductor memory device and to a fabrication method thereof.
2. Background of the Related Art
It is desirable to increase a storage capacity per unit area of a capacitor in view of the higher-integration trends in Dynamic Random Access Memories (DRAMs). Thus, a capacitor forming a DRAM memory cell employs a film including a material having a much higher dielectric constant relative to a silicon-based dielectric material that has been generally used.
FIG. 1A shows an example of a related art capacitor using a film having a high dielectric constant in a semiconductor memory device. The related art capacitor as illustrated in FIG. 1A is fabricated as follows. A semiconductor substrate 1 has an impurity layer 2 formed at its surface. An interlayer insulation film 3 is formed on the substrate 1 with a contact hole 4 therethrough exposing the impurity layer 2. The contact hole 4 is partially filled with a conductive material. A node contact 5 is formed to be connected with the conductive material in the contact hole 4, and is formed of a polycrystalline silicon. A diffusion barrier film 6 and a first electrode 7 on the diffusion barrier film 6 are formed at a predetermined region on the interlayer insulation film 3 including the node contact 5. A dielectric film 8 having a high dielectric constant is formed on the interlayer insulation film 3, upper and side portions of the first electrode 7 and side portions of the diffusion barrier film 6. A second electrode 9 is formed on the high dielectric constant film 8 to complete fabrication of the capacitor.
In the related art capacitor using the high dielectric constant film, the diffusion barrier film 6 prevents the first electrode 7 from reacting with the node contact 5, which consists of the polycrystalline silicon, while the first electrode 7 is formed of platinum or the like. In addition, the diffusion barrier film 6 prevents oxidation of the node contact 5 in an oxidizing atmosphere while forming the high dielectric constant film 8. Accordingly, the diffusion barrier film 6 is required to have a superior oxidation resisting property at a high temperature.
However, in the related art capacitor as shown in FIG. 1A, the sidewalls of the diffusion barrier film 6 are externally exposed, and thus directly exposed to the oxidizing atmosphere when the high dielectric constant film is formed. In addition, oxygen is diffused by a distance (d) in from the sidewalls. Thus, the node contact 5 consisting of the polycrystalline silicon is oxidized. To overcome the above-mentioned disadvantages, the diffusion barrier film may be formed at the inside of the node contact.
As shown in FIG. 1B, another related art capacitor has a diffusion barrier film 6xe2x80x2 formed at the inside of a node contact 5xe2x80x2. However, even in the related art capacitor as shown in FIG. 1B, a distance (dxe2x80x2) between the sidewall of the first electrode 7xe2x80x2 and the diffusion barrier film 6xe2x80x2 is generally less than 500A, which is similar to the oxygen diffusion distance (d) in the related art capacitor illustrated in FIG. 1A. As a result, it cannot prevent the node contact 5xe2x80x2 from being oxidized.
FIG. 1C is a cross-sectional view illustrating an interface of the diffusion barrier film 6 and the node contact 5 when the diffusion barrier film 6 and the first electrode 7 are mis-aligned in the related art capacitor as shown in FIG. 1A. In other words, in FIG. 1C the diffusion barrier 6 and the first electrode 7 deviate from a central axis of the node contact 5 and are asymmetrically formed in the related art capacitor as illustrated in FIG. 1A. As shown in FIG. 1C, when the diffusion barrier film 6 and the first electrode 7 are mis-alignied, the node contact 5 is externally exposed and the high dielectric constant film 8 is formed thereon, which results in inferior contact and current leakage. Thus, the above-described related art capacitors using a high dielectric constant film for a semiconductor device have various disadvantages.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the present invention is to provide a capacitor and method for forming the same that substantially obviates one or more disadvantages of the related art.
Another object of the present invention is to provide a capacitor and method for fabricating the same that provides a contact having an increased reliability.
Another object of the present invention is to provide a capacitor that increases a process margin for a first electrode position.
Another object of the present invention is to provide a capacitor using a high dielectric constant film and method for making the same that provides a contact having an increased reliability and an increased tolerance for electrode positioning.
In order to achieve at least the above-described objects of the present invention in a whole or in parts, there is provided a capacitor using a high dielectric constant film for a semiconductor memory device that includes a semiconductor substrate having an impurity layer at its surface; an interlayer insulation film formed on the semiconductor substrate and including a contact hole therethrough filled at an inner end portion thereof with a conductive material connected to the impurity layer; a first oxide film formed on an outer portion of 10 the interlayer insulation film; a nitride film formed on an outer portion of the first oxide film; a patterned second oxide film formed on a region of the nitride film; a diffusion barrier film formed on side portions of the second oxide film, outer and side portions of the nitride film where the second oxide film is not formed, side portions of the first oxide film, and an outer end portion of the contact hole; a first electrode formed on the diffusion barrier film; a high dielectric constant film formed on outer portions of the second oxide film, on outer portions of the diffusion barrier film, and on the first electrode; and a second electrode formed on the high dielectric constant film.
To further achieve the above-described objects of the present invention in a whole or in parts, there is provided a capacitor for a semiconductor memory device that includes a patterned first insulation film that exposes a top surface of a contact hole over a semiconductor substrate, a patterned second insulation film on the patterned first insulation film, a diffusion barrier film on side portions of the second insulation film, side portions of the first insulation film and the top surface of the contact hole, a first electrode on the diffusion barrier film, a dielectric film on outer portions of the second insulation film, outer portions of the diffusion barrier film, and the first electrode, and a second electrode on the dielectric film.
To further achieve the above-described objects in a whole or in parts, there is provided a method for manufacturing a capacitor according to the present invention that includes forming an impurity layer at an outer surface of a semiconductor substrate, forming an interlayer insulation film on the semiconductor substrate having a contact hole therethrough filled with a conductive material, wherein a bottom surface of the conductive material contacts the impurity layer, sequentially forming a first oxide film, a nitride film and a second oxide film on the interlayer insulation film so that a top surface of the conductive material is exposed therethrough, and wherein the nitride film and the first oxide film are partially exposed through the second oxide film, forming a diffusion barrier film at outer and side portions of the second oxide film, side portions of the nitride film, side portions of the first oxide film, and the top surface of the conductive material, forming a first electrode on the diffusion barrier film, removing the diffusion barrier film and the first electrode from an outer portion of the second oxide film, forming a high dielectric constant film on the outer portions of the second oxide film and the diffusion barrier film, respectively, and on the first electrode, and forming a second electrode on the high dielectric constant film.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.